The present invention provides a method and apparatus configured to determine an endpoint for a cleaning process for removing silicon and carbon based deposition byproducts using a two-step cleaning process where each step of the cleaning process is optimized for removing a byproduct. In one embodiment, the first step of the two-step cleaning process is optimized for removing silicon-based chamber byproducts and the OES wavelength integration bands associated with the products and reactants from the first step are monitored to determine an endpoint. The second step of the two-step cleaning process is optimized for the removal of carbon-based deposition byproducts and the OES wavelength integration bands associated with the products and reactants from the second step are monitored to determine an endpoint. It should be appreciated that the present invention can be implemented in numerous ways, including as an apparatus, a system, a device, or a method. Several inventive embodiments of the present invention are described below.
In one embodiment, a method for determining an endpoint of an in-situ cleaning process of a semiconductor processing chamber is provided. The method initiates with providing an optical emission spectrometer (OES) configured to monitor selected wavelength signals. Then, baseline OES threshold signal intensities are determined for each of the selected wavelength signals. Next, an endpoint time of each step of the in-situ cleaning process is determined. Determining an endpoint time includes executing a process recipe to process a semiconductor substrate within the processing chamber. Executing the in-situ cleaning process and recording the endpoint time for each step of the in-situ cleaning process are also included in determining the endpoint time. Then, nominal operating times are established for each step of the in-situ cleaning process.
In another embodiment of the present invention, a method for cleaning byproducts deposited on interior surfaces of a semiconductor processing chamber is provided. The method initiates with flowing an etchant process gas with a fluorine- containing compound of the formula XyFz, the fluorine-containing compound being optimized to remove silicon and silicon compounds. Then, a first plasma is formed from the etchant process gas to perform a silicon based cleaning step. Next, an emission intensity of an optical radiation from a reactant or a product in the first plasma is detected. Then, the silicon based cleaning step is ended after the emission intensity reaches a threshold value and when a slope of a trace of the emission intensity is about zero.
In yet another embodiment, a method for cleaning interior surfaces of a processing chamber is provided. The method initiates with flowing an etchant process gas with an oxygen-containing compound, the oxygen-containing compound being optimized to remove carbon and carbon compounds. Then, a first plasma is formed from the etchant process gas to perform a carbon based cleaning step. Next, an emission intensity of an optical radiation is detected from one of a reactant or a product in the first plasma. Then, the carbon based cleaning step is ended when a slope of a trace of the emission intensity is about zero after the emission intensity reaches a threshold value.
In still yet another embodiment of the invention, a plasma processing system for executing a two step in-situ cleaning process is provided. The plasma processing system includes a processing chamber having a gas inlet for introducing a cleaning gas. The cleaning gas is optimized to remove byproducts deposited on inner surfaces of the processing chamber. The processing chamber includes a top electrode for creating a plasma from the cleaning gas to perform an in-situ cleaning process. A variable conductance meter for controlling a pressure inside the processing chamber independently of a flow rate of process gases is included. The variable conductance meter is positioned on a outlet of the processing chamber. An optical emission spectrometer (OES) for detecting an endpoint of the in-situ cleaning process performed in the processing chamber is included. The OES is located so as to detect an emission intensity in the processing chamber from the plasma and the OES is configured to trance the emission intensity from the plasma. A pumping system for evacuating the processing chamber between processing operations is also included.
Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.